One of the most relevant topics in the biology of invasion concerns the genetic changes that occur subsequent to a species invasion, an issue of particular focus among conservation biologists. Colonizing a novel environment presents a genetic challenge to invading species because such species surely have not experienced the selective pressures presented by the environment. Here we ask, by what mechanisms and processes do alien species genetically naı¨ve to their new environment, become successful invaders? We attempt to resolve this paradox by considering the interplay between an invader's ability to modify its new environment, and genetic modifications imposed by the new environment. We postulate that epigenetic adaptations, and adaptive mutations are likely play a role in enhancing invasion success.
Abstract.-This paper describes the karyotype ofOdontesthes regia by means of Giemsa staining, C-banding, to reveal the distribution of the constitutive heterochromatin, and by Ag-staining and fluorescent in situ hybridization (FISH), to locate ribosomal genes (rDNA). The chromosome diploid modal count in the species was 2n = 48. The karyotype is composed of one submetacentric pair (pair 1), 16 subtelocentric pairs (pairs 2 to 17), and 7 acrocentric pairs (pairs 18 to 24). With the exception of pair 1 it was not possible to classify the homologous chromosomes accurately because differences in chromosome size were too slight between adjacent pairs. The distribution of C-banded heterochromatin allowed for a more accurate matching of the majority of chromosomes of the subtelocentric series. Silver staining of metaphase spreads allowed for the identification of Nucleolus Organizer Regions (Ag-NOR) on pair 1. FISH experiments showed that 18S rDNA sequences were located, as expected, in the same chromosome pair identified as the Ag-NOR-bearing one.Key words: Karyotype, NOR, C-bands, FISH
Resumen.-Este trabajo describe el cariotipo deOdonthestes regia, por medio de tinción Giemsa, bandeo C, para revelar la distribución de la heterocromatina constitutiva, y por medio de tinción con nitrato de plata e hibridación fluorescente in situ (FISH), para localizar genes ribosomales (rADN). El recuento modal cromosómico diploide en la especie fue de 2n = 48. El cariotipo está compuesto por un par submetacéntrico (par 1), 16 pares subtelocéntricos (pares 2 al 17) y 7 pares acrocéntricos (pares 18 al 24). Con excepción del par 1, no fue posible clasificar con exactitud a los cromosomas homólogos, ya que las diferencias en el tamaño fueron muy pequeñas entre pares adyacentes. La distribución de la heterocromatina por bandeo C permitió aparear a la mayoría de los cromosomas de la serie subtelocéntrica. La tinción con plata de preparaciones metafásicas permitió la identificación de las regiones organizadoras del nucléolo (Ag-RON) en el par 1. Los experimentos FISH mostraron que las secuencias ADNr 18S estaban localizadas, como era de esperar, en el mismo par cromosómico identificado como los portadores de Ag-RON.
ABSTRACT. This work describes the progress made in farming of Chilean silverside (Basilichthys microlepidotus), on the basis of broodstock captured in 2012 in the Mataquito River. A total of 179 individuals (adults and juveniles) were captured using a fishing rod fitted with a hook. The broodstock were transported to IFOP´s Experimental Center in Huihue-Chiloé for reproductive conditioning. Following a period of 18 months, the individuals distributed in different farming units reached the gonad maturation stage and spawned naturally. The eggs collected hatched after remaining 16 days in incubation under laboratory conditions. The group of newly hatched larvae displayed lengths around 8.0 ± 0.2 mm, reached lengths close to 18.5 ± 2.8 mm, 30 days of culture (post-hatching). Larvae harvesting took place in tanks with filtered and sterilized freshwater. The reabsorption of the vitelline vesicle was followed by digestive tract development, stage at which the larvae started to be fed with live food (Artemia nauplii), complemented with a commercial feed supplement. The growth of the larvae was described until 45 days post-hatching and following 266 days of culture, close to 45% of the larvae reached the juvenile stage (11.3 ± 2.6 cm). This paper deals with aspects related to larvae survival and the introduction of improvements to streamline larvae and juvenile production in order to upscale the culture of this species at the commercial level (aquaculture diversification), in addition to exploring the possibility of carrying out repopulation programs with juveniles. Keywords: Basilichthys microlepidotus, Chilean silverside, broodstock, spawning, larvae, aquaculture.Avances en el cultivo del pejerrey chileno Basilichthys microlepidotus Jenyns, 1841: una alternativa para la diversificación productiva RESUMEN. Se describe los avances en el cultivo del pejerrey chileno (Basilichthys microlepidotus), a partir de la captura de reproductores realizada durante el 2012 en el Río Mataquito. Un total de 179 peces (adultos y juveniles) fueron capturados utilizando una caña de pescar provista de anzuelo. Los peces capturados fueron trasladados para su acondicionamiento reproductivo a las instalaciones ubicadas en el Centro Experimental que mantiene IFOP en Huihue-Chiloé. Luego de 18 meses los ejemplares distribuidos en diferentes unidades de cultivo alcanzaron el estado de madurez gonadal y desovaron de forma natural. Los huevos recolectados lograron eclosionar luego de permanecer 16 días en incubación en condiciones de laboratorio. El grupo de larvas recién eclosionadas presentó longitudes cercanas a los 8,0 ± 0,2 mm, alcanzando luego de 30 días (post-eclosión) de cultivo tallas de 18,5 ± 2,8 mm. El cultivo larval se desarrolló en estanques con suministro de agua dulce filtrada y esterilizada. Después de la reabsorción del saco vitelino se produjo el desarrollo del tracto digestivo, momento en que las larvas comenzaron a ser alimentadas con una dieta de alimento vivo (nauplius de Artemia), complementada con un suplemento alimentici...
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